Methods absorbing energy using plastically deformable coil energy absorber

ABSTRACT

In an embodiment, a method of absorbing energy comprises: impacting a portion of a vehicle comprising a coil energy absorber, and compressing and plastically deforming the coil energy absorber. The coil energy absorber has an initial height and is located between the support structure and the covering, and wherein the coil energy absorber absorbs energy upon impact such that, after the impact, the coil energy absorber has a final height that is less than or equal to 90% of the initial height. The coil energy absorber is made of plastic. The coil energy absorber is located between a fascia and a support structure of the vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/724,962, filed on Mar. 16, 2010, which is herein incorporated byreference in its entirety.

BACKGROUND

This disclosure relates to energy management systems for pedestriansafety and vehicle damageability, and especially relates to energyabsorber systems that employ plastic deformation.

Increased importance has been placed on methods for minimizing theamount of injury suffered by a pedestrian when struck by a vehicle.Focus has been on bumper assemblies, headlamps. For bumper assemblies,foam resins have been used for energy absorption. Foam based systemstypically have slow loading upon impact resulting in a highdisplacement. Further, while foams are effective to a sixty or seventypercent compression, beyond that point foams become incompressible suchthat the impact energy is not fully absorbed. The remaining impactenergy is absorbed through deformation of a backup beam and/or vehiclestructure. Foams are also temperature sensitive so that displacement andimpact absorption behavior changes substantially with temperature.Typically, as temperature is lowered, the foam becomes more rigid,resulting in higher loads to attain displacement. Conversely, astemperature rises, foams become more compliant resulting in higherdisplacements and possible vehicle damage.

With respect to headlamps, actually, due to their placement at the frontor the corners of the vehicle, the headlamps of the vehicle are one ofthe locations most contacted by a pedestrian in an impact, or damaged inan impact with another vehicle. Several different designs have beenproposed for minimizing pedestrian injury during an impact as well asminimizing damage to headlamps (e.g., headlights). Some of them requiresignificant structural modifications to the headlamp which increase itsvolume, weight, and/or cost. Others require structural modification tothe chassis surrounding the headlamp area.

In the current competitive automotive market, a major challenge for adesign engineer is to reduce component mass, thus reducing the systemcost and increasing the fuel efficiency. At present, original equipmentmanufacturers (OEMs) are very aggressive regarding lower energy absorbermass as the available alternative system provides low cost and low masssolution but with a compromise in performance.

What is needed in the art are energy management systems that meet thedesired impact targets at reduced mass (as compared with standard energyabsorber systems currently on the market), and, where possible, reduceor simplify vehicle repairs.

BRIEF DESCRIPTION

The above-described drawbacks are alleviated by the present energymanagement system comprising springs that can deform plastically.

In an embodiment, a method of absorbing energy comprises: impacting aportion of a vehicle comprising a coil energy absorber, and compressingand plastically deforming the coil energy absorber. The coil energyabsorber has an initial height and is located between the supportstructure and the covering, and wherein the coil energy absorber absorbsenergy upon impact such that, after the impact, the coil energy absorberhas a final height that is less than or equal to 90% of the initialheight. The coil energy absorber is made of plastic. The coil energyabsorber is located between a fascia and a support structure of thevehicle.

In another embodiment, method of absorbing energy comprises: impacting aportion of a vehicle comprising a coil energy absorber, and compressingand plastically deforming the coil energy absorber. The coil energyabsorber is made of plastic. The coil energy absorber is located betweena fascia and a support structure of the vehicle. The support structureis selected from a bumper beam, a body in white, a body in black, afront-end module, a radiator support beam, a bumper support bracket, acomponent projecting from the body in white, a component projecting fromthe body in black, and combinations comprising at least one of theforegoing. The vehicle meets EEVC WG17 Phase-II for upper leg impactand/or for lower leg impact.

In an embodiment, a method for energy management in a vehicle comprises:installing a coil energy absorber in a vehicle, wherein a coil energyabsorber is made of plastic and is located between a support structureof the vehicle and a covering. The support structure selected from abumper beam, a body in white, a body in black, a front-end module, aradiator support beam, a bumper support bracket, a component projectingfrom the body in white, a component projecting from the body in black,and combinations comprising at least one of the foregoing. The vehiclemeets EEVC WG17 Phase-II for upper leg impact and/or for lower legimpact.

The above described and other features are exemplified by the followingFigures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Refer now to the drawings, which are exemplary, not limiting, andwherein like elements are numbered alike in several figures.

FIG. 1 is a side view of an embodiment of a compression coil springcomprising a conical geometry.

FIG. 2 is a side view of an embodiment of a coil spring comprising aconical geometry, illustrating the change in diameter of the spring.

FIG. 3 is a side view of an embodiment of a coil spring comprising acylindrical geometry with a constant pitch.

FIG. 4 is a side view of an embodiment of a coil spring comprising acylindrical geometry with a variable pitch.

FIG. 5 is a side view of an embodiment of a coil spring comprising anhourglass geometry.

FIG. 6 is a side view of an embodiment of a coil spring comprising abarrel geometry.

FIG. 7 is a prospective view of an embodiment of springs attached to anupper bumper beam.

FIG. 8 is a prospective view of an embodiment of springs attached to alower bumper beam.

FIG. 9 is a prospective view of an embodiment of the back of a vehiclegrill, with the springs attached to the covering (e.g., fascia).

FIG. 10 is a prospective view of an embodiment of a spring comprising aplastic deformation element.

FIG. 11 is a side view of one embodiment of a spring comprising lockingelements, wherein the spring is in the open position.

FIG. 12 is a top view of the spring of FIG. 11 in the compressedposition and with the locking elements plastically deformed.

FIG. 13 is an embodiment of a thermoplastic energy absorber systemcomprising a C-section geometric configuration instead of compressionsprings.

FIG. 14 is a side view of a complete energy absorber system, e.g., abumper assembly.

FIG. 15 illustrates graphical results of a plastic compression springtested for static compression versus a CAE simulation.

FIG. 16 is a side view of a multi-stage energy absorber.

FIG. 17 is a front view of a winding process for use in producing a coilspring.

DETAILED DESCRIPTION

Energy management systems comprising plastically deformable compressionspring(s) can be used in various components within a vehicle system thatcan benefit from energy absorption. For example, plastic compressionspring(s) can be employed in bumper assemblies, light assemblies (e.g.,headlamp assemblies, rearlamp assemblies, interior lighting assemblies,and so forth), dashboard assemblies, hood restraint systems, fenderassemblies, roof assemblies, door module assemblies and/or steeringwheel assemblies. The plastically deformable compression spring(s) canprovide energy absorption, which, under the desired degree of energy fora particular area, becomes plastic deformation. Such systems can enabledirected tunability (e.g., stiffness at a specific location in a system,with different stiffness elsewhere), individual replacability(individual springs can be replaceable without requiring replacement ofthe entire component (e.g., replacement of a spring instead of thebumper assembly), reduced component weight, enable the bumper assembliesto meet or exceed pedestrian safety standards, and enhanced vibrationstability of the bumper system.

In some embodiments, the plastically deformable compression springs canbe employed as energy absorbers for automotive bumper assemblies. Suchassemblies offer improved pedestrian safety with respect to lower legmodel testing, upper leg model testing, and knee acceleration modeling,in addition to a reduced system cost by significantly reducing the massof the component, e.g., by up to 25%. The reduced mass of the energyabsorbers additionally aids in providing higher fuel efficiency byreducing the overall mass of a vehicle. The present system employs aplurality of plastically deformable springs across the bumper of avehicle. The amount of energy required to compress the springs can betuned (e.g., chosen), based upon several factors such as the type ofvehicle, governmental regulations/requirements, the location along thebumper where the spring is located (i.e., each spring can have the sameor different compression characteristics than another spring in thebumper). In other words, the bumper can be customized. For example, theenergy absorbers disclosed herein meet the requirements of the lower legimpact phase-2 targets with a 20% safety margin and also meet therequirements of the upper leg impact phase-2 regulations.

A great advantage of this system is that customization can be attainedeven without multiple types of tooling or equipment. The general designof every bumper assembly can be similar, e.g., with a fascia (e.g.,outermost portion of the bumper assembly), springs, and a backingelement (e.g., support structure). The difference between the systemscan be the specific springs employed. The springs can also be removablyattached, e.g., demountable, (i.e., can be removed and reattached to theelement to which they are attached, without damaging said element) tothe vehicle (e.g., to the fascia, to a bumper beam, to the body in white(BIW), to the body in black (BIB), bumper beam, a front-end module, aradiator support beam, bumper support brackets, a component projectingfrom the BIW, a component projecting from the BIB, and combinationscomprising at least one of the foregoing), enabling facile replacementof a spent spring e.g., after a collision. For example, the spring(s)can have a threaded portion enabling them to be threaded into theappropriate element of the bumper system which will comprise thecorresponding female component with mating internal threads. Otherpossible attachments include an opening into or through the particularelement wherein an end of the coil passes into or through the openingand is retained therein, as well as fasteners described below inrelation to fastening to the fascia.

Multiple springs (i.e., a set or a plurality of springs) can be placedover the full span of the vehicle to meet the performance targets ofpedestrian safety, and/or to enhance vehicle integrity and/or componentlongevity. In other words, it is envisioned that the springs can be usedin the front bumper system, the rear bumper system, and/or withinvarious elements of the vehicle (e.g., in the head lamps, fenderassemblies, hood restraint system, dash board assemblies, door moduleassemblies and roof assemblies).

A further advantage of the spring bumper system is that the replacementof a continuous shell-wall structured energy absorber with a set oftuned springs can reduce the system mass by greater than or equal toabout 25%, the raw material cost by greater than or equal to about 30%,the tooling cost by greater than or equal to about 30%, and can lowerthe replacement cost for the overall bumper beam assembly if damaged.These energy absorbers can also enhance the vibration stability of thebumper fascia by absorbing vibration and/or force applied to the bumperfascia.

As is noted above, the energy absorber system can comprise a fascia,coil springs (e.g., various geometry compression springs, also referredto as helical springs) that offers flexibility to tune for a desireddegree of plastic deformation during the impact; e.g., full plasticdeformation, partial plastic deformation. The desired degree of plasticdeformation is dependent upon various factors such as the impactcondition (e.g., to reduce pedestrian injury, to reduce occupant injury,to reduce vehicle damage, etc.), the location on the vehicle of theenergy absorber system, the type of vehicle, regulatory requirements,and others. Generally, the springs are designed to have a plasticdeformation of greater than or equal to 10%, specifically, greater thanor equal to 15%, and more specifically, greater than or equal to 20%. Insome embodiments, the plastic deformation can be 10% to 50%,specifically, 15% to 45%, and more specifically, 15% to 40%. In someembodiments, the plastic deformation can be greater than or equal to45%, specifically, greater than or equal to 50%, more specifically, 50%to 100%, yet more specifically 60% to 100%, and even more specifically,75% to 100%. Here, the percent of plastic deformation is understood tobe determined according to the following formula:h _(f) =h _(i)−(% p _(d))(h _(i))

wherein:

-   -   P_(d)=plastic deformation    -   h_(f)=final height (“h”) of the spring after the impact    -   h_(i)=initial height (“h”) of the spring before the impact

For example, for impact conditions where human body is involved, (e.g.,leg impact to vehicle bumper, or head impact over instrument panel orfender), a greater degree of plastic deformation is desired to absorbmore energy than to redirect the energy at the body, higher plasticdeformation (greater than or equal to 50% plastic deformation of thecoils is desired). In other words, for a spring having a height (“h”) of100 millimeters (mm), if the spring is designed for pedestrian injury,upon an impact, the spring would plastically deform greater than orequal to 50%. Therefore, the height of the spring would decrease bygreater than or equal to 50%. After the impact the spring height wouldbe less than or equal to 50 mm. For the impact condition where theobjective is to minimize damage to vehicle components, such as duringlow speed crashes, lower plastic deformation is generally desirable,e.g., a plastic deformation of greater than or equal to 15%,specifically, 15% to 40%. For example, if the energy absorber system isdesigned to reduce vehicle damage, for a spring having a height of 100mm, for a low speed crash (e.g., less than or equal to 16 kilometers perhour (km/hr) (10 miles/hour)), after the accident, the spring heightwould be 60 mm to 85 mm.

Metal springs absorb the energy of impact and then release the energy byexerting a force opposite to the force received; they spring back,thereby transferring the energy to the element struck (e.g., thepedestrian). As a result, metal springs have not been used in front ofbumper beams (e.g., have not been employed directly behind a fascia).These plastic springs, however, deform elastically, but also plastically(e.g., greater than or equal to 10% plastic deformation as describedabove), thereby tuning (e.g., controlling) the amount of energy releasedback toward the impact subject. Plastic springs dissipate the energyreceived instead of only projecting the energy back at the objectimpacted. They elastically and plastically deform. Hence, a bumpersystem has thermoplastic springs (e.g., wholly thermoplastic spring), ora combination of thermoplastic and non-thermoplastic springs (e.g.,springs comprising thermoplastic coil(s) and non-thermoplastic coil(s),springs comprising a core and a coating, wherein at least one of thecore and the coating is a non-thermoplastic material while the other isa thermoplastic material). Possible non-thermoplastic materials includethermoset material, metal, ceramic, and a combination comprising atleast one of the foregoing non-thermoplastic materials. These springscan be employed anywhere in the vehicle system without concern for theenergy release by the spring.

For example, to provide a controlled and energy efficient management forlower leg and/or upper leg impact, the bumper (e.g., the front of thebumper) can have a tuned stiffness profile (e.g., a different stiffnessin different locations to attain a desired energy absorption uponimpact). In one embodiment, the springs can be tuned locally to meet theperformance targets (e.g., near the middle portion of the bumperassembly versus near the ends of the bumper assembly). For example, thesprings can be tuned to have a stiffness of 0.01 kiloNewton permillimeter (kN/mm) to 10 kN/mm. Optionally, the springs can have astiffness gradient from the middle of the bumper assembly toward theends of the bumper assembly, with a higher stiffness toward the ends ofthe bumper beam (e.g., enabling a greater energy absorption in a smallerspace).

The compression springs can have various geometries. Some geometries areillustrated in FIGS. 1-6, including conical (FIGS. 1 and 2), cylindrical(FIGS. 3 and 4, hourglass (FIG. 5), barrel (FIG. 6). These springs canhave a constant or variable pitch (e.g., see FIGS. 3 and 4,respectively). The springs can be tuned during formation to meet theperformance targets. In still another embodiment, the springs can betuned after formation but prior to assembly to meet the performancetargets. The geometric parameters of springs like, length, coildiameter, wire diameter, pitch can be tuned for different stiffness,during formation. After formation of springs, their layout over supportstructure can be configured to achieve different stiffness profiles.

The stiffness of each spring can be further tuned by varying thediameter and/or the pitch (i.e., the angle or degree of inclination) ofthe coils. FIG. 2 illustrates the coil diameter (d_(c)). The stiffnesscan be tuned by increasing or decreasing the diameter of the coils,wherein an increase in diameter also increases the stiffness. Forexample, the coil diameter (d_(c)) is dependent upon the desiredstiffness, the distance that will be used between springs, the height ofthe springs, as well as other factors. In some embodiments, the coildiameter (d_(c)) can be 10 mm to 20 mm.

With respect to the spring diameter, the desired diameter is partiallydepending upon the shape of the spring (e.g., conical, cylindrical,barrel, etc.). For a conical spring, in some embodiments, the smallestdiameter end can have a diameter that is less than or equal to 50% ofthe largest diameter end, specifically, less than or equal to 35% of thelargest diameter end, more specifically, less than or equal to 25% ofthe largest diameter end, and yet more specifically, less than or equalto 20% of the largest diameter end. For example, the largest diameterend can have a diameter of 70 mm to 90 mm (e.g., 80 mm), while thesmallest diameter end can have a diameter of 10 mm to 20 mm (e.g., 15mm). In various embodiments, the pitch can be 10 mm to 60 mm,specifically, 15 mm to 40 mm, and more specifically, 20 mm to 30 mm.

Desirably, the materials of the springs are chosen to attain the desiredplastic and elastic deformation. In some embodiments, the plasticsprings can be totally thermoplastic (wherein “totally” means that thereare no non-thermoplastics added thereto, but impurities may be present),or the springs can comprise plastic and another material. For example,the plastic coil may comprise a metal core (e.g., a thin metal wirecoated in plastic), wherein the plastic deformation is provided by theplastic casing.

The spring can comprise any material(s) having the desiredcharacteristics for the particular application (e.g., desired stiffnessand plastic deformation) of the springs in the vehicle. With geometriclimitations such as length and diameter of the spring, the desiredstiffness of spring for different impact requirements can be achieved byselecting different material(s). Exemplary characteristics of thematerial include high toughness/ductility, thermal stability, highenergy absorption capacity, a good modulus-to-elongation ratio, andrecyclability, among others, wherein “high” and “good” are intended tomean that the characteristic at least meets vehicle safety regulationsand requirements for the given component/element. The springs cancomprise a non-metallic material that is capable of plastic deformation(e.g., a plastically deformable non-metallic portion and a metallicportion). Exemplary spring materials include polycarbonate, polyester(e.g., polybutylene terephthalate (“PBT”), polyethylene terephthalate(“PET”), and others), as well as combinations comprising at least one ofthe foregoing materials. For example, the spring can comprise XENOY™resin(s) which is commercially available from SABIC Innovative Plastics.In some embodiments, the plastic material can be a thermoplasticmaterial that is flexible at temperatures of −60° C. to 200° C. Forexample, unfilled thermoplastic materials can have a tensile strength of0.5 gigaPascals (GPa) to 2.8 GPa, a yield of 5 megaPascals (MPa) to 70MPa, and/or an elongation of 10% to 150%; and filled thermoplasticmaterials can have a tensile strength of 1.5 GPa to 10 GPa, and/or anelongation of 0.5% to 10%; while composite materials (e.g., laminates)can have a tensile strength of 80 GPa to 160 GPa, and/or a shear modulusof 70 MPa to 100 MPa. For example, blends of polycarbonate/polybutyleneterephthalate (e.g., a particular XENOY™ resin, commercially availablefrom SABIC Innovative Plastics IP B.V.) can be employed, having atensile strength of 1.87 GPa, a yield of 48 MPa, and an elongation of120%.

Exemplary thermoplastics include polycarbonate, polybutyleneterephalate, polypropylene, acrylonitrile-butadiene-styrene (ABS),acrylic-styrene-acrylonitrile (ASA), polyester (e.g., PBT, PET),polyamides, polyethylene (e.g., low density polyethylene (LDPE), highdensity polyethylene (HDPE)), polyamides, phenylene sulfide resins,polyvinyl chloride (PVC), polystyrene (e.g., high impact polystyrene(HIPS)), polypropylene (PP), polyphenylene ether resins, andthermoplastic olefins (TPO), and combinations comprising at least one ofthe foregoing. Some additional examples of plastic materials that can beused for the springs include, but are not limited to, polycarbonate/ABSblends, a copolycarbonate-polyester,acrylonitrile-(ethylene-polypropylene diamine modified)-styrene (AES),polyphenylene oxide and polystyrene (e.g., glass filled blends ofpolyphenylene oxide and polystyrene), blends of polyphenyleneether/polyamide, blends of polycarbonate/polyethylene terephthalate(PET)/polybutylene terephthalate (PBT), blends ofpolycarbonate/polybutylene terephthalate, polyethylene and fibercomposites, polypropylene and fiber composites, long fiber reinforcedthermoplastics, and combinations comprising at least one of theforegoing plastic materials. Commercially available materials includeLEXAN™ resins, LEXAN™ EXL resins, XENOY™ resins, NORYL GTX™ resins,NORYL™ resins, and VERTON™ resins commercially available from SABICInnovative Plastics, as well as AZDEL Superlite™ sheets commerciallyavailable from AZDEL, Inc. Optionally, e.g., to further enhance tuningof the overall bumper assembly, different springs in the energy absorbersystem can comprise the same or a different material(s).

Turning now to FIGS. 1 through 6, different embodiments of the springsdescribed herein are illustrated. FIGS. 1 and 2 illustrate an embodimentwhere the springs are of a helical, conical shape, while FIG. 3illustrates a constant pitch, cylindrical shaped spring, FIG. 4illustrates a variable pitch, cylindrical shaped spring, FIG. 5illustrates an hourglass shaped spring, and FIG. 6 illustrates a barrelshaped spring. The springs comprise a coil diameter (d_(c)), a springdiameter (d_(s)), a height (h), and a pitch (p). These features areillustrated in FIGS. 2 and 3. In some embodiments, as illustrated inFIG. 2, the coil spring can have a conical geometry featuring a firstcoil (22) adjacent to a second coil (24) where the first coil (22) hasan outer diameter that is less than or equal to an inner diameter of thesecond coil (24). In one embodiment, the spring (10) is configured toplastically deform upon the application of energy to the fascia (16)(i.e., the spring deforms upon impact and does not return to itsoriginal shape after the impact is finished). As can be seen in FIGS.1-6, the interior of the spring can be open; a void. Optionally, theinterior can comprise a material or component that can assist inretaining the spring in its compressed position.

Turning now to FIGS. 7 through 9, a plurality of springs (10) are shownwhere the springs (10) are attached to a support structure (12, 14). Thesupport structure (12, 14) can comprise an upper bumper beam (12) and alower bumper beam (14). FIGS. 7 and 8 illustrate an embodiment where thecoil spring (10) has a conical geometry where inner and outer diametersof the coils gradually increase as the coils get closer to the supportstructure (12, 14) (i.e., the spring has a conical geometry thatdiverges toward the support structure). FIG. 7 illustrates an embodimentwhere a first portion of the plurality of coil springs (26) are locatedon the upper beam portion (12) and a second portion of the plurality ofcoil springs (28) are located on the lower beam portion (14).

In one embodiment, as shown in FIG. 8, the support structure (14)comprises a support element (20). The support structure (12, 14) cancomprise a component located on a front portion of a vehicle (e.g., acomponent having sufficient stiffness to support a desired compressionof the springs upon a predetermined impact). The component (e.g., “stiffcomponent”) can be selected from the group consisting of a bumper beam(e.g., a steel bumper beam), a front end module (e.g., a componentlocated behind a front bumper assembly), a radiator support beam, bumpersupport brackets, a component projecting from body in white, as well ascombinations comprising at least one of the foregoing. Generally thesupport structure is the body in white (BIW) and/or a component attachedto the BIW. In various embodiments, the support structure (12, 14) canbe chosen and/or designed to have sufficient structural integrity toenable the coil spring to fully compress.

FIGS. 7 and 8 illustrate a plurality of coil springs (10) designed overthe full length of the vehicle bumper (front and/or rear) where thesprings (10) are tuned locally to meet the desired performance targets.In one embodiment, the desired stiffness as estimated from a lumpedparameter model (e.g., a model that uses spring, mass, and dampers) canbe achieved with greater than or equal to 5 springs (10). The springs(10) can be located between the fascia and the BIW, and can be attachedto (e.g., located on, mounted or connected to) the fascia, the bumperbeam (and/or another support structure located between the spring andthe BIW), as well as any combination thereof. The springs (10) can bearranged such that a first spring (30) is parallel to a second spring(32). In one embodiment, the springs (10) can be located on a plate(e.g., a rigid plate, i.e., a plate that does not deform during theimpact and transfer maximum load to spring for compression) for uniformload distribution where the plate is attached to a support memberlocated on the front or the rear of the vehicle where the bumperassembly is attached.

In some embodiments, the number of springs (10) in the bumper assemblycan be greater than or equal to 7, specifically, greater than or equalto 10, more specifically, greater than or equal to 20, and yet morespecifically, greater than or equal to 25. In still other embodiments,the number of springs (10) in the bumper assembly can be 1 to 20,specifically, 3 to 15, more specifically 5 to 10, and yet morespecifically, 5 to 7. As noted, the springs can be aligned along thesupport element and/or fascia in a row (e.g., straight row), or can bestaggered. Also, more than one row of springs can be disposed betweenthe fascia and the support element (e.g., the multistage spring absorberillustrated in FIG. 15), wherein a support structure can be locatedbetween the rows of springs in order to enable the springs to compressas desired.

FIG. 9 illustrates an embodiment of the back of a vehicle grill wheresprings (10) are attached to a fascia (16). The fascia (16) is adecorative element of the bumper assembly that covers or encloses thesprings (10) and other components of the bumper assembly. As isillustrated in this figure, in some embodiments, the springs (10) canattach to the fascia (16) as opposed to other elements of the bumperassembly, or in addition to other element(s) of the bumper assembly. Ifthe springs (10) attach to the fascia (16), the fascia can comprisefascia securement(s) (56) such as hook(s), slot(s), fixture(s),clamp(s), clip(s), screw(s) and bolt(s), U-clamp(s), as well as otherfastener(s), and the like, e.g., on an inner surface (58) of the fascia(16). For example, an end of the spring (10) can be disposed through thefascia securement (56) and can be configured to inhibit inadvertentwithdrawal from the fascia securement (56). Withdrawal can be inhibitedin various fashions, including, for example, a hook, bend, enlargedportion, or element (60) near the end of the spring (10) that preventswithdrawal of the spring (10) from the fascia securement (56). Forexample, the fascia securement can be disposed through a hole (e.g., aring) located near the end of the spring. The fascia securements (aswell as other elements for attaching the springs to the vehicle), can bedesigned to enable the removal and replacement of individual springs,i.e., without requiring replacement of the element to which the springis attached.

In some embodiments as illustrated in FIGS. 10-12, locking mechanism(s)can be employed in conjunction with one or more of the springs. Somepossible locking mechanism(s) include a locking element (66) that, oncecompressed retains the spring in the compressed position. Illustrated isan arm (68) in operational engagement with the support element (20)(e.g., bumper beam). At or near one end of the arm 68 is a plate orrestrainer (70), while the portion of the arm extending through thespring (10) and into the support element (20) comprises protrusion(s)(72) (e.g., snap-fit elements, barbs) that allow the arm (68) to move ina direction “D” upon the application of a force to plate (70). As thearm (68) moves in direction “D”, toward the support element (20), theprotrusions (72) pass through an opening (74), in the support element(20), wherein the protrusions (72) are sized and designed to allowpassage through the opening (74) in the “D” direction, and to inhibitthe passage of the protrusions (72) back through the opening (74) in theopposite direction. In other words, when a sufficient force pushes theplate (70) toward the support element (20) and to force protrusions (72)through the opening (74), the locking element (66) then retains thespring (10) in the compressed (or partially compressed) position.

FIGS. 11 and 12 illustrate additional locking elements that can be usedalone or in conjunction with the element of FIG. 10. In these Figures, aplastic element (e.g., a plastic sheet (34)) is in operationalcommunication (e.g., connected to) with the coils of the spring (10).During compression and energy absorption, the plastic sheet (34) servesto absorb some of the energy, causing the sheet(s) (34) to plasticallydeform. The plastic deformation of the sheet(s) further locks the coilsin the compressed position, thus preventing the coils from springingback into their original position and expressing the force back outward.For example, during impact, the sheet (34) can experience all plasticdeformation rather than elastic deformation, while the spring (10) canexperience both plastic and elastic deformation.

The plastic element can be formed of the same or a different material asthe spring. For example, the plastic element can be formed fromthermoplastic (e.g., unfilled thermoplastics having good ductility). Insome embodiments, the plastic sheet can be an integral part of thespring (i.e., non-detachable from the spring), e.g., made of samematerial. In other embodiments, it can be designed as a separatecomponent (e.g., that can be located in operational communication withthe spring (such as attached to the spring)). Optionally, the plasticelement can be detachable from the spring and configured to plasticallydeform before the spring plastically deforms. Hence, when the impact isonly sufficient to plastically deform the element, the plastic elementcan be detached and replaced, e.g., without requiring replacement of thespring. The size of the plastic element is dependent upon the desiredplastic deformation characteristics and material used. In variousembodiments, the thickness of the plastic element can be up to about 4millimeters (mm) or so, e.g., 0.5 mm to 4 mm.

FIG. 14 illustrates one embodiment of a bumper assembly (36). In FIG.14, a spring (10) (e.g., a coil spring) is attached to a supportstructure (42) which is located in front of a radiator (40). A fascia(16) encloses the spring (10) and support structure (42) where thefascia (16) is located between a hood (38) and an undercarriage (44).The spring (10) is located between a support structure (42) (i.e., thebumper beam) and the fascia (16) and is configured to compress uponapplication of energy to the fascia (16). Upon the application of forceto the fascia (16), the spring (10) compresses and experiences plasticdeformation such that when the force ceases, the spring (10) is lockedinto place and does not spring back (i.e., the spring does not returnback to its original shape before compression). Depending upon theamount of force and the design of the spring, the plastic deformationcan inhibit a portion or all of the elastic action of the spring). Forexample, in some embodiments, the spring remains partially compressed,only returning to less than or equal to 80% of its original height, “h”,specifically, less than or equal to 65% of its original height, morespecifically less than or equal to 50% of its original height, and yetmore specifically, less than or equal to 25% of its original height. Insome embodiments, the spring can remain fully compressed. In someembodiments, however, when the force is less than that needed toplastically deform the particular spring, when the force ceases, thespring returns to its original shape (e.g., to greater than or equal to95% of its original height, “h”).

FIG. 16 illustrates one embodiment of a multistage, plastic spring,bumper assembly (46). In FIG. 16, a plurality of springs (48) isillustrated as attached to a support structure (42) which is located infront of a radiator (40). A fascia (e.g., a cover plate) (50) surroundsthe plurality of springs (48) and support structure (42) where thefascia (50) is located between a hood (38) and an undercarriage (44).The plurality of springs (48) is located between a support structure(42) and the fascia (50) and is configured to compress upon theapplication of energy to the fascia (50). In the illustrated embodiment,the plurality of springs (48) is arranged in series and in parallel formulti-stage energy absorption. A first set of springs (52) is locatedbetween the fascia (50) and the support structure (76), while a secondset of springs (54) is located between the support structure (76) andthe support structure (42). It is understood that although two sets ofsprings are illustrated in series, the assembly can comprise one or moresets of springs (e.g., greater than or equal to 2 sets of springs,specifically, greater than or equal to 3 sets of springs) arranged inseries, between the fascia and a support structure (e.g., the bumperbeam), with support structures located between each set of springs. Eachset of springs can have the same or a different compressibility (e.g.,stiffness) than any other set of springs.

Upon application of energy to the fascia (50), the springs (10) willbegin to compress. The stages can be designed to compresssimultaneously, or sequentially. In some embodiments, for example, thefirst set of springs (52) will begin to compress and after a certainthreshold compression, the second set of springs (54) will begin tocompress. For example, the second set of springs (54) can begin tocompress when the first set of springs (52) has compressed to less thanor equal to 25% of their original height (h), specifically, less than orequal to 40%, more specifically, less than or equal to 50%, yet morespecifically, less than or equal to 75%, still more specifically, lessthan or equal to 80%, even more specifically, less than or equal to 90%,and even, less than or equal to 95%, of their original height (h).

The coil springs (10) as disclosed herein can be manufactured via anyprocess suitable for processing thermoplastic materials. For example,the plastic material can be extruded into a shape (e.g., a rod,cylinder, tube, roll, etc.). In one embodiment, the thermoplastic rodcan be wound around a cylinder (e.g., a steel cylinder), to produce thecoil springs described herein. For example, the diameter of rod can becontrolled during extrusion process using different dies, the overalldiameter of the spring can be fixed on the steel mandrel diameter, andthe pitch of the spring can be tuned during winding process changing thespeed of coil winding. The coil springs (10) can be processed by hotwinding (e.g., FIG. 17), cold winding, as well as other processes. Theconical helical coils can also be manufactured by injection moldingprocess. The winding process includes less tooling cost compared toinjection molding process, while the injection molding process is moresuitable for mass production.

The arrangement of springs over the support structure (i.e., the springlayout) plays a role in tuning the stiffness profile of a bumper system.Springs arranged in close proximity to each other offer higher stiffnessto the bumper system than the same type of springs (e.g., same shape,size, etc.) arranged far apart from each other. The appropriate spacingbetween springs can be identified such that enough support can beoffered to a lower leg impactor for impact at locations between thesprings. Spacing between sets of springs in the vertical direction canbe tuned according to the vehicle height and knee location of the lowerleg from the ground. The position of each spring in the layout can befixed for tuning the bumper stiffness locally (i.e., at each individualvehicle assembly plant). An optimum layout can vary from vehicle tovehicle, depending on vehicle bumper parameters (e.g., the layout canvary depending on the type of vehicle used; the layout can vary if thevehicle is a small, compact vehicle, versus a larger sport utilityvehicle). Springs can be arranged close enough to offer support to thelegform hit at an intermediate location between the springs. They canalso be sufficiently spaced to minimize mass.

Different combinations of spring arrangements (e.g., in series and inparallel as illustrated in FIG. 16) can help achieve multistage energyabsorption behavior. For example, consider FIG. 16, which illustrates anexample where dual stage energy absorption can be achieved by using aset of softer springs in a first stage (52) and a second set of stiffersprings in a second stage (54). The first stage springs (52) and secondstage springs (54) can be separated with the help of a spacer or plate(e.g., support structure (76)) based on vehicle bumper parameters andthe need to meet impact requirements of different geographic locations,an optimum combination/arrangement can vary from vehicle to vehicle.

The plastic spring energy absorber is further illustrated by thefollowing non-limiting examples.

EXAMPLES Testing Procedures

The following results were obtained using computer aided engineering(CAE) methodology.

The coil spring energy absorber system is validated over a genericvehicle platform. First, a set of plastic springs are mounted over anupper cross-car beam and a second set of plastic springs are mountedover a bumper beam. All the components of the vehicle front bumpersystem up to the A-Pillar are considered in the CAE model (e.g., thefascia, grille, hood, fenders, headlamps, beam, undertray, radiatorassembly, etc.).

The vehicle bumper system incorporating a plurality of helical conicalplastic springs is impacted with a commercially available lower legmodel and a knee acceleration model, i.e., G-load in units of gravity(g), knee bending (i.e. rotation in degrees (deg)), and tibia shear inmillimeters (mm) are estimated by CAE model using LS-DYNA software(commercially available from Livermore Software Technology Corp,Calif.).

The vehicle bumper system incorporating sets of helical conical plasticsprings is impacted with a commercially available upper leg model andthe maximum force, measured in kiloNewtons (kN), and the maximum bendingmovement measured in Newton meters (N·m) are estimated for the upper legmodel, which is a CAE model developed by Ove Arup & Partners, Coventry,UK

Comparative Example 1

Comparative Example 1 is an energy absorber design as illustrated inFIG. 13 comprising energy absorbing elements. This design is a variantof thermoplastic energy absorbers with a C-section geometry comprisingXENOY®, a thermoplastic material comprising polycarbonate andpolybutylene terephthalate, commercially available from SABIC InnovativePlastics. The support structures, upper cross-car beam, and bumper beamdesigns are the same as for those described for mounting in Example 1.The performance numbers for lower leg impact and upper leg impact areestimated using the same methodology as described with respect toExample 1.

Comparative example 1 is an optimum C-section energy absorber design,made of XENOY® thermoplastic material, designed for minimum possiblemass through injection molding process, meeting lower leg impactPhase-II targets. The energy absorber was mounted on the same supportstructure as used for Example 1. The conventional energy absorber wasalso designed to meet Phase-II targets. Thus the comparison was betweentwo designs developed to meet Phase-II targets for same vehicleplatform.

Example 1

Example 1 is an energy absorber design comprising conical, helical,plastic springs disposed across a steel bumper beam as illustrated inFIG. 7. The springs had a diameter at their base of 80 mm, a diameter atthe top of 25 mm, a coil diameter of 15 mm, and a depth (e.g., heightfrom the base to the top) of 80 mm. The springs were formed from a blendof polycarbonate and polybutylene terephthalate (e.g., XENOY®commercially available from SABIC Innovative Plastics).

TABLE 1 G- Rota- Max. Bending Exam- Impact Mass load tion Sheer ForceMovement ples (at Y = 0) (kg) (g) (deg.) (mm) (kN) (N · m) Comp. LowerLeg 2.0 110.6 2.2 4.8 — — Ex. 1 Ex. 1 Lower Leg 1.5 94.8 <1 1.7 — —Comp. Upper Leg 2.0 — — — 6.84 333.9 Ex. 1 Ex. 1 Upper Leg 1.5 — — —4.87 268.2

The results comparing the thermoplastic energy absorber (Comp. Ex. 1) tothe plastic spring design (Ex. 1) are set forth in Table 1. As is clearfrom Table 1, the use of the helical spring enabled, for the upper leg,a reduction in bending movement of greater than 50 Newton-meters (N·m),and a reduction in force of nearly 2 kiloNewtons (kN) (i.e., thethermoplastic energy absorber exhibited 40% more force and nearly 25%more bending movement). With respect to the lower leg, with the springs,the G-load was reduced by more than 10 grams, the rotation was reducedby more than a degree, and the shear was reduced by more than 2 mm, ascompared to the thermoplastic energy absorber. In other words, comparedto the spring design, the thermoplastic energy absorber comprising aC-section geometry exhibited greater than 115% G-load, greater than 220%rotation, and greater than 280% sheer.

The designed helical conical spring energy absorber system is observedto meet the EuroNCAP lower scale values for lower leg impactrequirements and to meet the EEVC WG17 Phase-II requirements for lowerleg impact, i.e., G-load <150 (G (gravitational force)), knee bending<15 degrees, and tibia shear <6 mm. Also, the performance numbers areobserved to be within the lower limit of the EuroNCAP scale for upperleg impact requirements (i.e., 150 (G), 15 degrees, and 6 mm), andwithin the EEVC WG17 Phase-II requirements for upper leg impact, i.e.,Force of less than 5 kN (kiloNewtons) and Bending moment of less than300 Nmm (Newton millimeters).

Example 2

Prototype samples were prepared to validate the CAE studies. From theseprototypes, component level tests were conducted. Commercially availablepolypropylene material was used to develop prototype samples. Thepolypropylene rods were heated below the melt temperature, and windedover a wooden mandrel manually to form helical conical coils. Acompression test was performed in a Universal testing Machine (UTM) anda force versus deformation curve was compared with the CAE studies ofcompression phenomenon in Example 1 and Comparative Example 1 utilizingthe same parameters. FIG. 15 displays a descent correlation between theCAE examples, line 92 (Comparative Example 1 and Example 1) and Example2, line 90. A simple compression test was performed for developed coilsusing a UTM. One end of the coil was fixed with the help of jaws, andthe coil was compress at the free end by a steel plate moving with aspeed of 6 millimeters per minute (mm/min.). The same test procedure wasreplicated in a CAE where one end was constrained and at the free endwas compressed by a rigid plate moving with a speed 6 mm/min. Theresults shown in FIG. 15 increase the confidence on CAE simulationsconducted for system level studies for lower leg and upper leg impactcases.

The energy management systems disclosed herein enable novel geometricconfigurations (e.g., of bumper assemblies), material and processing,while able to achieve multi-stage energy absorption. The flexibility totune elastic and plastic deformation of the springs gives an edge overother energy absorbers and over metal springs. These systems enable areduction in system mass and material cost, a reduction in tooling cost,and an efficient energy management in minimum space. Although thesesprings could be used with shell wall structures (e.g., such asillustrated in FIG. 13), they can be used independently, replacing theshell wall structure, thereby reducing mass. Furthermore, they can betuned to enhance vibration stability of the fascia.

In one embodiment, an energy management system can comprise: supportstructure(s) (e.g., a vehicle support structure); a fascia; and aplastically deformable compression spring(s) located between the supportstructure and the fascia. In another embodiment, an energy managementsystem can comprise: support structure(s) (e.g., in a vehicle); acovering(s); and plastically deformable compression spring(s) locatedbetween the support structure(s) and the covering(s). A method ofabsorbing energy can comprise: impacting a portion of a vehiclecomprising the energy management system (e.g., on a fascia of a vehiclebumper system) and compressing and plastically deforming the compressionspring(s) to form compressed spring(s). A method for energy managementin a vehicle can comprise: installing an energy management system in avehicle.

In the various embodiments: (i) the support structure (e.g. a metalbumper beam, metal plate, steering column, etc.) can have sufficientstructural integrity to enable the compression spring(s) to fullycompress; (ii) the covering can be the outer most element of the energyabsorber system (e.g., such that there is no additional structuralcomponent between the compression spring(s) and the object impacted(e.g., person, other vehicle, etc.)); (iii) the covering can be afascia; (iv) the spring can have a conical geometry such that a firstcoil is adjacent to a second coil and the first coil has an outerdiameter that is less than or equal to an inner diameter of the secondcoil; (v) the spring can be connected to the support structure; (vi) theenergy absorber system can comprise sets of springs (e.g., arranged inseries); (vii) the support structure can be a bumper beam comprising anupper beam portion and a lower beam portion, and wherein a firstplurality of compression springs can be located on the upper beamportion and a second plurality of compression springs can be located onthe lower beam portion; (viii) the support structure can be selectedfrom the group consisting of a bumper beam, a front-end module, aradiator support beam, bumper support brackets, a component projectingfrom body in white, and combinations comprising at least one of theforegoing; (ix) the compression spring(s) can be located on the supportstructure; (x) the springs can have a stiffness of 0.01 kiloNewtons permillimeter to 10 kiloNewtons per millimeter; (xi) the spring(s) can havea conical geometry that diverges toward the support structure; (xii) thespring(s) can be attached to the fascia; (xiii) spring(s) can beattached to the fascia and other spring(s) can be attached to thesupport structure; (xiv) the spring(s) can comprises a material selectedfrom the group consisting of a thermoplastic, a thermoplastic composite,and combinations comprising at least one of the foregoing; (xv) thespring(s) can further comprises a metal core (e.g., some can comprise ametal core, some can be a single material, and/or some can have a voidin the core (e.g., be hollow)); (xvi) the spring material can comprise athermoplastic and a metal; (xvii) the spring(s) can be thermoplasticwith a metal core; (xviii) the spring(s) can have a combination ofthermoplastic coils and metal coils; (xix) an inner diameter of thespring(s) can be a void; (xx) the compression spring(s) can have apercent plastic deformation upon impact of greater than or equal to 10%,specifically, greater than or equal to 15%, more specifically, greaterthan or equal to 20%, yet more specifically, greater than or equal to50% (e.g., 15% to 40%); (xxi) the compression spring(s) can be removablyattached to the support structure and/or covering.

In the various embodiments: (i) the spring(s) can comprise lockingelement(s) that will inhibit the spring(s) from returning to itsoriginal position after compression (e.g., the locking element(s) can beplastically deformable and/or can mechanically restrain the spring(s));(ii) the locking element(s) can have a percent plastic deformation uponimpact of greater than or equal to 20%, specifically, greater than orequal to 40%, more specifically, greater than or equal to 75%); (iii)the locking element(s) can comprise a non-metallic element (e.g., aplastic element) in operational communication with the spring(s); (iv)the locking element(s) can be configured (e.g., designed and located) tomechanically restrain the spring(s) after the energy absorber system hasbeen impacted; and/or (v) the locking element(s) can comprise a materialselected from the group consisting of polycarbonate, polybutyleneterephalate, polypropylene, acrylonitrile-butadiene-styrene, polyester,acrylic-styrene-acrylonitrile, polyethylene terephthalate, polyamides,polyethylene, and combinations comprising at least one of the foregoing.

The various methods can further comprise: (i) mechanically restrainingthe compressed spring; (ii) replacing the compressed spring while notreplacing the support structure; and/or (iii) plastically deformingdifferent springs in the energy management system by a different percentplastic deformation.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. The patentable scope of the inventionis defined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they have structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral language of the claims.

All ranges disclosed herein are inclusive of the endpoints, and theendpoints are independently combinable with each other (e.g., ranges of“up to 25 wt %, or, more specifically, 5 wt % to 20 wt %”, is inclusiveof the endpoints and all intermediate values of the ranges of “5 wt % to25 wt %,” etc.). “Combination” is inclusive of blends, mixtures, alloys,reaction products, and the like. Furthermore, the terms “first,”“second,” and the like, herein do not denote any order, quantity, orimportance, but rather are used to distinguish one element from another.The terms “a” and “an” and “the” herein do not denote a limitation ofquantity, and are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The suffix “(s)” as used herein is intended to include both thesingular and the plural of the term that it modifies, thereby includingone or more of that term (e.g., the film(s) includes one or more films).Reference throughout the specification to “one embodiment”, “anotherembodiment”, “an embodiment”, and so forth, means that a particularelement (e.g., feature, structure, and/or characteristic) described inconnection with the embodiment is included in at least one embodimentdescribed herein, and may or may not be present in other embodiments. Inaddition, it is to be understood that the described elements may becombined in any suitable manner in the various embodiments.

What is claimed is:
 1. A method of absorbing energy, comprising:impacting a portion of a vehicle comprising a coil energy absorber, andcompressing and plastically deforming the coil energy absorber; whereinthe coil energy absorber has an initial height and is located between asupport structure and a covering; wherein the coil energy absorberabsorbs energy upon an impact such that, after the impact, the coilenergy absorber has a final height that is less than or equal to 90% ofthe initial height; and wherein the coil energy absorber is made ofplastic.
 2. The method of claim 1, further comprising mechanicallyrestraining the coil energy absorber.
 3. The method of claim 1, whereinthe plastic is selected from the group consisting of a thermoplastic anda thermoplastic composite.
 4. The method of claim 1, wherein the coilenergy absorber has a conical geometry that diverges toward the supportstructure.
 5. The method of claim 1, wherein the coil energy absorberare configured to have a stiffness of 0.01 kiloNewtons per millimeter to10 kiloNewtons per millimeter.
 6. The method of claim 1, wherein thesupport structure is selected from a bumper beam, a body in white, abody in black, a front-end module, a radiator support beam, a bumpersupport bracket, a component projecting from the body in white, acomponent projecting from the body in black, and combinations comprisingat least one of the foregoing.
 7. The method of claim 1, wherein thefinal height is less than or equal to 50% of the initial height.
 8. Themethod of claim 7, wherein the final height is 0 to 40% of the initialheight.
 9. The method of claim 8, wherein the final height is 0 to 25%of the initial height.
 10. The method of claim 1, wherein the coilenergy absorber has a conical geometry such that a first coil isadjacent to a second coil and the first coil has an outer diameter thatis less than or equal to an inner diameter of the second coil.